THE 


P I i O G R Ji e 


OF THE 


Metallurgy of Gold and Silver 


IN THE 


XJIsriTEID STATES, 


By T. EGLESTON, Ph.D. 

M 

From Vol. Ill, School of ?>1ines (^caktehly. 


NEW YORK, 1882. 


// 


-'M- 






ERRATA. 


Page 40, line 17, foi-, in the last number of the Quarterly, p. 80, 
read p. 10. 



C. ts :j».J <■* ' ’’ ■■' 


\:frt 





THE 


PROGRESS OF THE METALLURGY 

OF 

GOLD AND SILVER 

IN THE 

UNITED STATES. 


BY T. EGLESTON, Ph.D. 


The progress of metallurgy in the United States during 
the last thirty years has not only been very rapid, but has 
produced very extraordinary results. Previous to the discovery 
of gold in California in 1848 , the United States produced but a 
small portion of the world's product of metals, and its people 
were not known as skilled in the mining or metallurgical sciences. 
The great coal-fields were known and worked, and iron was pro¬ 
duced in what would now be considered very small quantities. 
The discovery of copper on the upper peninsula of Lake Supe¬ 
rior, and of gold in California, showed the want of knowledge 
of these subjects amongst our people, and undoubtedly gave the 
stimulus to the energy and enterprise which now makes the 
United States one of the greatest of mining and metallurgical 
nations. Twenty-five years ago there was no place in the 
United States where an elementary knowledge of either mining 
or metallurgy could be had in any of the educational institutions 
of the country. To-day a more thorough knowledge of these 
sciences can be had here than anywhere else. The prospector of ♦ 
these early days has been obliged to give way to the thoroughly 
trained mining and metallurgical engineer. No finer or better 




2 THE METALLURGY OF GOLD AND SLLVER. 

examples of what skill and science can do are to be found than 
the works which have been erected in different sections of the 
United States within the last fifteen years. In the early days^ 
when prospectors and mineral wands were more or less relied 
on, “ science,” which meant education in general, was looked on 
with suspicion ; the demand was for “ practical men.” But as 
soon as it became apparent that there was enormous wealth in 
the ground which could not be extracted by half-educated men 
with empirical means, science was called in. In the first few 
years the “ scientific cuss,” as he was called, was expected to be 
a mining, metallurgical, mechanical, and chemical engineer, and 
in all cases where he did not know, to improvise his knowledge; 
but it was not long before experts in all these branches were 
to be had, and, in consequence, new methods and new processes 
have resulted, so that mining and metallurgy have made more 
progress on this side of the Atlantic in the last thirty years, 
than had formerly been made in the Old World in more than 
one hundred. A quality of mind seems to have been produced 
by the mixture of races on this continent, which, while demand¬ 
ing for the people as a whole the most general information, ena¬ 
bles us to easily grasp details, while the eminently mechanical 
genius of our people leads us to adapt, improve, and invent 
machinery for every purpose, and thus, by replacing hand labor, 
to both improve and cheapen the cost of processes. 

The gold excitement in 1848 was produced by the discovery • 
of the very rich placer mines on Sutter Creek, Amador Co., 
California, from which the gold in quite large pieces was easily 
separated by washing with water in a common pan. Shortly 
after, the discovery of a number of nuggets of large size,^ and 


^ A list of the large nuggets is not without interest. One of 3000 lbs. was re¬ 
ported to have been found in the West Indies and sent to Spain in a ship which 
never reached its destination. 

NUGGETS FROM AUSTRALIA. 


Sarah Sands, 1850 (?).... 

.223 lbs. 4 oz. 

Old Daisy Hill, 1855.... 


Ballarat, 1853. 

.184 “ 8 “ 

Ballarat, 1855. 

.. 48 

f 4 

( i # 4 ( 

•135 ” 

Bendigo, 1852. 

.. 47 

4 4 

Blanche Barkley, 1842 (?). 

.146 “ 6 “ 

Ballarat, 1855. 

.. 40 

4 4 

Two, 1849. 

.112 “ 

Bendigo, 1852. 


4 4 . 4 4 

4 

One, 1851. 

.106 “ 

Dascombe, 1852. 

.. 28 

% 4 

Maryboro, 1855. 

Fryer’s Creek, 1855. 

CO CO 

• • 

Mt. Blackwood, 1855... 

.. 24 

« 4 


URAL MOUNTAINS. 

•Near Miask, Siberia, 1842.96 lbs. One.27 lbs. 

In 1878.78 “ Several of...16 “ 


6 ^ 


i vt 























THE METALLURGY OF GOLD AND SLLVER. 


3 


the rumor that others had been found and cut into small pieces 
to prevent their value being known, caused the wildest enthu¬ 
siasm all over the United States. Some large fortunes were 
made among the crowd of adventurers who rushed to California, 
but no one can know of the misery and disappointment caused 
by this wholesale emigration. The success of the few was widely 
published, but the record of the failures was never made. What 
they must have been is shown by the fact that after the State of 
California had provided insane asylums for the percentage usual 
in other States, the authorities were obliged to double their 
capacity.^ 

So entirely has mining formed a part of the history of the 
country, that the very words which express the miner’s joy or 
sorrow, his success or failure, have passed into the current con¬ 
versation of society. To “ strike it rich,” to “ find pay,” to “ pan 
out,” or to “ get down to hard-pan” or “ to the bed-rock,” indi¬ 
cate to the people of the Western coast their success or failure, 
their prosperity or adversity, more emphatically than any other 
words in the English language could do. 

It is very doubtful whether the Western States and Territo¬ 
ries would have been settled even now but for the fabulous yield 
of the early discovered surface deposits. California had been 
more or less occupied for two hundred years by Spaniards and 
Mexicans. It was known in a general way that gold was to be 
found either in that country or districts adjacent to it. Shal¬ 
low placers had been worked with very small results for a long 
time. Placer gold was discovered and worked in 1841.“ In 
1843 gold-bearing quartz had been worked. But the discovery 


PARAGUAY. 

One of 50 lbs. 

, PERU. 

In 1730, one of 45 lbs. 


UNITED 

California, Calaveras Co., 1854.. 160 lt)S. 


“ Sierra Co.106 “ 

“ “ 1869. 95 i “ 

N. Carolina, Reed Mine. 80 

California, Sierra Co., 1871 (not 
authenticated). 64 “ 


In England several nuggets of 40 o 
None have been found in Brazil. 

* I have this statement from a former 

* Engineering and Mining Journal, vc 


STATES. 

N. Carolina, Cabarrus Co., 1838. 37 lbs. 

California, Sierra Co.32 “ 

“ Georgetown, 1865... 17 “ 

N. Carolina, Anson 1829. 10 “ 

California, Nevada Co. 8 “ 

mces have been found, but none larger. 
Treasurer of the State of California. 

1. 32, p. 170- 










4 THE METALLURGY OF GOLD AND SILVER. 


of gold in the sluice of a mill depopulated, for the time being, 
the city of San Francisco, brought a small population from 
China, and thousands from Mexico; but the country was in a 
very few months taken possession of by men from the Eastern 
States, attracted there both by the fabulous stories about the 
gold and by their love of adventure. Everybody who could 
dig (and who could not ?) became at once a miner. It was not 
an unfrequent thing, so rich were the deposits, for men who 
could not earn more than seventy-five cents a day where they 
came from, to make several hundred dollars between sunrise and 
sunset, with the rudest appliances, and with a loss of no one 
knows how much gold beside. This great gain was, however, 
of but little use to him, because, having acquired it without 
much labor, no special value was attached to it, and he spent it 
as freely as he found it. The price of everything in California 
was, consequently, very high.^ Trade was carried on as barter, 
in which “ gold dust,” as it was called, which was of all sizes, 
from a nugget the size of the fist to an impalpable powder, an¬ 
swered the purpose of a medium of exchange. In every-day 
life the fine material was used in the place of coin. It was car¬ 
ried by the miners in buckskin bags which were opened for the 
merchant to take his own pay by repeatedly taking out what 
he could hold between his thumb and forefinger. A single 
pinch from the bag was considered to be equal to twenty-five 
cents, which was the lowest value recognized ; two pinches were 
equivalent to fifty cents, four to one dollar, and so on. The 
honest (?) merchant of those days kept his forefinger pressed 
on a conical button in his waistcoat, in order to make a de¬ 
pression in it, so that the intrinsic value of the single pinch was 
often equal to a dollar, or even more. This was of no conse¬ 
quence whatever to the miner, who did not condescend to weigh 
his gold, except in the case of nuggets or of large payments 
or bank deposits. 

At first, only the shallow and very rich placer mines were 
worked. They required no capital, and but an extremely lim¬ 
ited amount of intelligence and skill to work them. So long as 
they were easily found and the pay abundant, the separation of 
the gold was only approximative, and no special improvement 
was made in the processes of extraction. If the sand was very 

' Flour, $7.50 per pound ; butter, the same ; a barrel of pork, $210 ; a bottle 
Cf ale, $5 ; a candle, $3 ; a tin pan, $9. 


THE METALLURGY OF GOLD AND SILVER. 


5 


rich and water was not easy to be had, it was simply winnowed 
in a blanket, and what the wind did not blow off was amalga¬ 
mated when mercury could be procured, or it was panned in a 
rough way when water could be had, or was approximately 
picked out when there was neither water nor mercury. Any 
method was used without regard to loss, so long as the pay 
was made rich enough to transport, and could be sold by 
assay. * 

By such rude methods only a very small percentage of the 
gold was extracted, but it would cost trouble to get it all out, so 
it was left where it was. The miner was then careless of his 
mode of working, giving no thought to the future, and was 
extravagant in his habits and methods. In less than five years 
after its first discovery, the quantity of gold had reached a 
maximum, and after 1853 began to decrease steadily. As the 
amount of gold diminished the methods of extracting it im¬ 
proved ; the miners became aware that they were losing gold, 
and little by little they ascertained that this loss occurred in 
several different ways: either it was not separated from the 
lumps of sand or clay and was carried off with them, or it 
was so thin in the pay rock or became so thin in the process 
of extraction that it was buoyed up and carried off by the 
water, or was lost because the gold for some reason did not 
amalgamate. At first he simply called this light gold “float” 
and the other “ rusty,” and made no very great account of 
it. But as it became evident that a very large proportion of 
the gold in the “ pay” was being lost in this float and rusty 
gold, he became anxious first to ascertain how much there 
was that he did not catch and what part of this was float— 
a material so light that it was carried off upon the water, and 
was thus swept away—and what part was rusty, that is, did not 
amalgamate with the mercury. To determine this he sought 
for machines to work with. The miner’s pan had up to this 
time been the tool with which he “ got the color,” which is the 
expression used when the gold begins to appear after washing 
the pay dirt in a pan; but when he found that he must have 
other appliances, the miner of 1848 took the processes Avhich he 
found in use by the Mexicans and the Mexican Indians in Cali¬ 
fornia, and adopted them bodily. These were, the miner’s pan,, 
which he adopted when he first came into the country, and con¬ 
tinued to use so long as the placers were very rich ; the arastra, 
and the Chilian mill upon which so much ridicule has been cast 


6 THE METALLURGY OE GOLD AND SLLVER. 


in later times, and to the principle of which we shall probably 
have to come back as the gold grows scarcer. The rude methods 
of concentration associated with these machines were the only 
methods that he found there, and these he accepted without at 
first thinking of any improvement. 

With the altered condition of affairs every experiment that 
want of experience or an active imagination could suggest was 
tried. Every man improvised himself a miner, and felt it his 
bounden dutv to commence where Tubal-cain did, but without 
his intelligence. The sum of all that is left of these experiments 
is the sluices, riffles, and undercurrents which are still in use. 
They alone represent the activity and energy which in the first 
few years produced hundreds of failures and brought loss and 
disappointment, and in many cases ruin, to thousands of men. 
But the necessities of the case had so stimulated the active 
minds who brought their energies to bear on the subject that 
the failures were individual, as the loss of wealth of a country 
which no one owned was not estimated, and consequently was 
not felt. The country reaped the benefit of all these efforts 
and all the gains, and in consequence has made greater strides 
in the way of progress, and more improvement in thirty years 
than has ever been made in a century by any other nation. 

It is impossible to estimate the losses which must have oc¬ 
curred in these early days by such rough methods of working. 
The “ Forty-niners,” as they are called, cared very little whether 
they got out all the gold. What they did care for was to make 
the greatest present profit not only between the first and last of 
the month, but between sunrise and sunset of every day. Sunday 
did not count for a holiday then. It was of no consequence to 
the miner what he lost, but it was of great importance to him 
what he gained. He recognized only to-day ; he knew and cared 
nothing about the time when through his slovenly methods gold 
would become scarce, and if he knew that he was losing gold 
his regret was for himself because he did not get it, and not 
that the country was a loser. He knew nothing about political 
economy, and would have cared nothing for it if he had. He 
was extravagant in his habits, generous to a fault, careless of 
his methods, entirely satisfied to let the future take care of it¬ 
self. By the time that the placers began to grow less productive 
the population of the country had increased to such an extent 
that, labor becoming abundant and wages so comparatively low, 
the necessity of living, which Talleyrand declared not to be 


THE METALLURGY OF GOLD AND SILVER. 7 


necessary, became a stimulus towards improvement in the pro¬ 
cesses and to the effort to save what had been previously con¬ 
sidered as not worth saving. More careful washing made men 
look for a more abundant water supply. The freer use of mer- 
cnry enhanced its value and set the prospectors searching for 
mercury mines.^ 

Our present methods, which are being constantly improved, 
appear extravagant to those who have been trained in the Euro¬ 
pean schools, because they do not take into consideration the 
fact that with a rate of wages much higher than in Europe, 
and with transportation at its maximum, their economies would 
cost‘more to carry out than they would yield. Hence the for¬ 
eigner coming to this country has generally to commence his 
education here by unlearning some parts of the knowledge which 
he has been taught to consider as his first principles, before he 
begins to acquire the new ideas which are essential to his suc¬ 
cessful practice among our mines and metallurgical works. 

There is in this country no impediment to progress and im¬ 
provement, as there is in Europe in what is known as ancient 
legislation, where antiquated processes have become customs, 
and their use precedents not to be easily set aside. Their stat¬ 
ute books are full of laws preserving the rights of the govern¬ 
ment, of John Doe and Richard Roe, in certain specific things, 
and requiring in certain defined cases the following of ancient 
precedents or the use of obsolete processes and methods, the laws 
being made with reference to a condition of things which existed 
perhaps one hundred, three hundred, or even five hundred years 
ago, and remaining still unrepealed. It is undoubtedly in prin¬ 
ciple a wise precaution not to allow the investment of capital in 
mining enterprises without having the whole question both in a 
commercial and industrial point of view examined by govern¬ 
ment officers, and the government sanction given or withheld 
according as in the judgment of its officers it should or should 
not be given ; but it places a great deal of power in the hands 
of individuals who desire to hold the leading-strings, and does 
away with the individuality of enterprise which is one of the 
chief characteristics of our nation. The anxiety to prevent the 
individual loss in Europe often retards the prosperity of a whole 

^ The discovery of very large deposits of the ores of mercury in California, 
and the original process invented there for working it, are even more remarkable 
than the progress made in the working of the other metals. See Engineering 
London, vol. 28. p. 239. 


8 THE METALLURGY OF GOLD AND SLLVER. 


country, while the precedents as well as the written and unwrit¬ 
ten laws of some of the older countries, and the system of 
centralization in their governments which entrusts everything 
belonging to the government to corps or to the heads of bureaus 
at the seat of government, are great impediments to progress. 
In this country we are at liberty to deal with the necessities 
of the case as they occur. The impediments to progress are 
not too much but too little law, not ancient but conflicting legis¬ 
lation. These impediments are, however, incident to any new 
order of things, and it will not be many years before the last of 
these difficulties will be removed. 

When shallow placer-mining became less remunerative, the 
question of transportation commenced to be a factor in the 
question of production. While a miner was earning $TOO a day,, 
the fact that he was forced to “ pack ” every article he pur¬ 
chased for use as well as his gold on a mule to be carried for 
days or weeks, or concealed his treasure about his person and 
travelled on foot a considerable distance to invest or deposit his 
dust, was a matter of very little consequence in view of the large 
amount so easily earned.^ 

But when he was reduced to “ hard-pan” and only earned a 
little more than was necessary for the sustenance of life, the 
question both of improved processes and of transportation be¬ 
came a very serious one, and had to be studied very carefully. 
At this point he either improvised himself an engineer of mines^ 
and withTready Yankee Wit devised some process which would 
save “ the color,” or transported himself and his “ outfit,” which 
in those days meant what he could carry on his back, with his 
pick, spade, pan, horn or spoon, or more probably all of them, to 
some locality which was not so far removed from civilization. 
Others on the. contrary sought in localities farther from civiliza¬ 
tion richer pay diggings. 

It was not long before this continued migration produced its 
results, for while the miner at first searched only for gold and 
worked for gold alone, when it became scarce and the necessity 
of living became to him imperative, translating 'itself into the 
gnawings of hunger, other things became valuable besides gold,. 

* The s-afety and almost impunity with which large amounts were carried about 
the person in the early days of California mining was owing to the rapidity with 
which the vigilance committees of those days executed justice, which was not only 
speedy but severe. There were then no lawyers to impede the progress of what 
was almost invariably real justice, and death was usually the penalty inflicted. 


THE METALLURGY OF GOLD AND SILVER. 


9 


and he then stopped in his transit from one district to another 
in search of the precious metal to locate a silver deposit, some- 
times in the shape of lead ores, but he never noticed iron or 
copper. It was not until long after that he made the discovery 
that copper ores frequently carry gold. 

PLACER MINING. 

The deposits of gold first worked were called placers. These 
were at first recognized as the dry and the wet, the dry being 
either ancient river deposits or recent river beds from which the 
water was gone. The wet placers were streams which were 
sometimes large rivers. In these placers the gold was within 
twenty feet or so of the surface. The dry placers were worked 
with pans and sluices ; the rivers containing the wet placers 
were dammed and the whole of the water turned into flumes or 
sluices. The river mud was then sluiced. As it was impossible 
to keep the river bed dry, both because the dam leaked and because 
the surface drainage could not be kept out, large wheels called 
“ flutter wheels” were placed in the artificial channels, which 
pumped the water out of the river bed and furnished a sufficient 
supply of it to the sluices. Such workings were hazardous and 
expensive, for if the stream was at all large a single freshet 
might wash out the dam and the flume which carried the river. 
To make sufficient room to work and also to get enough 
ground to justify the expense, the flume carrying the water of 
the river was never less than two hundred and fifty yards and 
sometimes nearly a mile long. Such works were very expensive 
and somewhat hazardous, but sometimes yielded a very large 
profit. They were constructed by companies during the early 
days when the miners used less engineering skill and were 
willing to take more risks. Very few of these river claims 
exist now, and this kind of mining is already a thing of the past. 

As the placers grew poorer the gold was sought deeper, and 
it was then discovered that there were placers where the depth 
of the deposit was over three hundred feet, where the gold on 
the surface sometimes yielded only a few cents to the cubic yard,, 
but was rich on the bed-rock, hence the name of deep placers. 
Only shallow or surface placers and deep placers are now recog¬ 
nized. It is estimated that two thirds of all the gold produced 
in the world is taken from placer deposits. 

It is quite as impossible to form any adequate idea of the 


lo THE METALLURGY OF GOLD AND SILVER. 


amount of gold produced during these first periods of mining as 
it is to estimate the losses. No attempt was made to make any 
record at the time. The records of the custom-houses are the 
only ones made, and are necessarily imperfect; they show that 
between 1848 and 1854 over $350,000,000 had been recorded, 
but previous to that time very large sums had been carried away 
by those going either to Europe or to the East,* either in their 
effects or on their persons, and while the amount carried by an 
individual was small, the aggregate must have been very large. 
In the next decade more perfect records, were made, which show 
a gradual decrease, the highest point having been reached in 
1853 when the amount recorded is $65,000,000, and the lowest 
.$26,000,000 in 1864, the total amount for the decade being 
$450,000,000. The next decade to 1874 shows a product of 
only $220,000,000, the lowest amount reached being $17,000,- 
000 in 1873. This rapid decrease gives a very fair idea of the 
amount which must have been wasted within the first seven 
years of the most prosperous time, when the records, tho 
very imperfect, give an average of $50,000,000 a year, while the 
year 1873, when the records were most perfect, gave only $17,- 
000,000. From 1873 to the end of 1880 the total product of the 
State of California was $135,113,000; the lowest annual product 
being $15,000,000 in 1877, and the highest $18,000,000 in 1874. 
The following tables, showing the amount in each year, have 
been prepared for me by the Director of the Mint at Wash¬ 
ington. 


Year. 

Gold in Dollars. 

Year. 

Gold in Dollars. 

California. 

Other States. 

Total Gold. 

California. 

Other States. 

Total Gold. 


$ 

$ 

$ 


$ 

$ 

$ 

1848 

10,000,000 


10,000,000 

1865 

28,500,000 

24,725,000 

53,225,000 

1849 

40,000,000 


40,000,000 

1866 

25,500,000 

28,000,000 

53,500,000 

1850 

50,000,000 


50,000,000 

1867 

25,000,000 

26,725,000 

51,725,000 

1851 

55,000,000 


55,000,000 

1868 

22,000,000 

26,000,000 

48,000,000 

1852 

60,000,000 


60,000,000 

1869 

22,500,000 

27,000,000 

49,500,000 

.1853 

65,000,000. 

65,000,000 

1870 

25,000,000 

25,000,000 

50,000,000 

.1854 

60,000,000 


60,000,000 

1871 

20,000,000 

23,500,000 

43,500,000 

1855 

55,000,000:. 

55,000,000 

1872 

19,000,000 

17,000,000 

36,000,000 

1856 

55,000,000 


55,000,000 

1873 

17,000,000 

19,000,000 

36,000,000 

1857 

55,000,000 


55,000,000 

1874 

18,000,000 

15,490,902 

33,490,902 

1858 

50,000,000 

I 

50,000,000 

1875 

17,000,000 

16,467,856 

33,467,856 

1859 

50,000,000 


50,000,000 

1876 

17.753,000 

22,176,166 

39,929,166 

i860 

45,000,000; 1,000,000 

46,000,000 

1877 

15,000,000 

31,897,390 

46,897,390 

1861 

40,000,000 

' 3,000,000 

43,000,000 

1878 

15,260,000 

35,946,360 

51,206,360 

1862 

34,700,000 4,500,000 

39,200,000 

1879 

17,600,000 

21,299,858 

38,899,858 

1863 

1864 

30,000,000 

26,600,000 

10,000,000 

19,500,000 

i 

40,000,000 

46,100,000 

1880 

17,500,000 

18,500,000 

36,000,000 













































THE METALLURGY OF GOLD AND SLLVER. ii 


It is remarkable that while up to i860 there was almost no 
gold produced in the Eastern States, and that while in that year 
only $1,000,000 is reported, between i860 and 1870 the amount 
produced gradually increased, until in 1866 it exceeded it, and 
only fell so as to equal it in 1870. In the next decade, from 
1870 to 1880, the largest amount produced in all the other 
States except California was $35,946,360 in 1878, and the lowest 
$15,490,902 in 1874; with the exception of 1874 and 1875 the 
Eastern States produced more than California, and in 1878 more 
than double the amount produced there. The total yield of 
gold in the United States in the year 1880 was only $36,000,000, 
or less than that produced by California alone up to 1862, with 
the single exception of the year 1848. 

It is extremely difficult to ascertain the amount of gold con¬ 
tained in the world, and it may be said that the best estimates 
from the most reliable authorities are but the merest approxi¬ 
mations. It is supposed, however, that the entire amount of 
gold in existence at the present time is not over $7,000,000,000. 
As the value of a cubic yard of gold is $9,000,000, if all this gold 
were melted into one mass it would contain about 700 cubic 
yards, which would make a block about 25 by 25 by 31 feet, 
or less than the cubical contents of an ordinary small city 
house. 

Long before the fact that the gold was decreasing became 
known to the miners, it was evident that some new system 
would have to be used to extract it. The miner’s pan, a house¬ 
hold utensil, was used not because it was the best adapted to 
the work, but because it was the most available. It was an ex¬ 
ceedingly rude apparatus. It was made of sheet-iron from four 
to five inches deep. It was filled two thirds full of dirt, and put 
into a hole about one foot deep filled with water, and the con¬ 
tents of the pan well stirred with the hands; the pan was then 
taken in both hands, inclined slightly outward, and shaken so as 
to give a circular motion to the contents. The fine material 
flows in this way over the sides. When this has been done long 
enough, the stones are removed, any lumps of clay are broken 
with the hand ; then depressing the outer edge, it is shaken until 
nearly everything but the black sand is out of the pan. This is 
•separated by blowing. It required great skill, and gave a large 
loss in gold. It is now rarely used except for an assay for color, 
for which the shovel can also be used. The pan was used for a 
long time after other machines were introduced, but it soon 


12 


THE METALLURGY OF GOLD AND SLLVER. 


became necessary to have other implements. As an instrument 
for concentration, it was succeeded by the cradle or rocker, 
which was not unlike a child’s cradle, whose maximum capacity 
was 5 to 6 cubic yards of earth a day. It required two men to 
work this cradle efficiently, one to rock and pour on water, and 
one to bring the pay dirt and the water, whose weight was at 
least three times that of the dirt. The pay dirt was thrown 
upon a screen whose object was to separate the large stones and 
to help to break up the clay; the purpose of the water was to 
take up the finely divided particles. The concentrates are then 
panned. A pan contains about half a cubic foot of pay dirt. 
A one-man rocker could concentrate from lOO to 150 pans a 
day, and a two-man rocker twice as much. It is a very slow 
machine, must always be placed near the water, no matter what 
the distance of the pay dirt is, and even when used with quick¬ 
silver loses a very large amount of fine gold and all the float 
gold. 

The cradle was succeeded by the ‘‘long Tom,” which for 
nearly two years seemed a great improvement. It consists of a 
rough trough or launder eighteen feet wide at the upper end 
and thirty feet at the lower, and twelve feet long. The lower 
end is terminated by a screen of iron whose edge is so high that 
the water does not flow over it, but drops with its contents into 
a trough below provided with riffle bars and mercury. The pay 
is thrown in at the upper end and mixed with water; what 
passes the screens comes in contact with the mercury and is 
caught, but much of the fine and all the float gold is lost, 
tho it is a better machine than the cradle. As many as four 
men can work at a Tom, but it is now rarely seen. 

At the same time a puddler was used, which was a barrel cut 
in half or a rough wooden box six to eight feet square, and twelve 
inches high, with an inch and a half hole four inches from the bot¬ 
tom. The pay was thrown into this and broken up and mixed with 
the water until it was all in suspension. When the plug was re¬ 
moved, the thin mud was allowed to run out and the operation 
commenced again, and so on. The gold was collected in the 
bottom. The puddler never was used in this country except in 
small claims where water was scarce, but has been very success¬ 
fully and extensively used in other countries where water was 
not abundant. 

The next improvement was the sluice, which, altho it had 
been formerly used elsewhere, is as much a California invention 


THE METALLURGY OF GOLD AND SILVER. 


13 


as if it had never been used before it was invented here. It 
consists of a trough or launder made of rough one and a half 
inch boards sawn for the purpose, and nailed together without 
any pretence of making them fit, as it becomes tight by the 
swelling of the wood and the filling up of the cracks. The sluice 
is composed of a series of boxes, as they are called ; each box is 
twelve feet long, sixteen to eighteen inches wide at one end, and 
twenty to twenty-four at the other. The height of the sides 
varies from eight to twenty-four inches, according to the kind 
of material to be used in it. The narrow end of one box fits into 
the wide end of the other. The length of the sluice is estimated 
in boxes; it should not be less than fifty feet long, and often 
consists of hundreds of boxes put together supported on rough 
trestles. The inclination is regulated according to the neces¬ 
sities of the case, and is called the “ grade,” which always has ref¬ 
erence to the box. It is usually eight inches for a minimum and 
thirty inches for a maximum in twelve feet, or the length of a 
box. It is generally uniform, but sometimes is made to conform 
somewhat to the lay of the ground. The tougher the dirt, the 
longer and steeper the sluice must be. With a rapid descent 
the dirt is also much more easily separated, but the greater is the 
loss in gold. The boards are not only rough on the bottom and 
sides, but to prevent too rapid wear, and also to help to catch 
the gold, strips of wood are fastened in the bottom of the box, 
either in the direction of its length, which is most usual, or 
across it. These pieces of wood are from two to four inches 
thick, and from four^to six inches wide. When longitudinal 
they are six feet long, so that two sets go in a sluice. The riffles 
are wedged in so that they can be easily removed for a clean-up 
or for repairs. The bottom of each box is thus filled with a 
screen of rectangular cavities which are the width of the distance 
between the riffles, and haye their length and depth. Here the 
quicksilver which is put in at the head of the sluice rests and 
catches the gold as it sinks in the more or less rapid current. The 
water is generally made to run two inches deep over the riffles. 
The pay dirt is thrown in with shovels. The first dirt, which is 
always poor, goes to fill up the spaces between the riffles. The 
water, washing over this, washes out the earth and clay, the sand 
and gravel, and even the stones. No mercury is added until after 
the sluice has been running about two hours. It is then put in 
at the head and finds its way down the sluice, most of it being 
caught not far from where it is put in. One man can throw in 


14 THE METALLURGY OF GOLD AND SLLVEK. 


from two to five cubic yards of dirt a day. The number of men 
that can work depends on the length of the sluice and the lay of 
the ground. Sometimes when the earth to be washed contains 
large stones, an undercurrent is used. The end of the sluice is- 
then open. It terminates with a grating of iron bars long, 
enough to allow all the water to pass with the fine material 
through the grating, but allows the stones to roll out on the 
ground. The whole of the water and dirt is caught in a 
short sluice below and discharged into one parallel with the 
main sluice, which is thus continued. This undercurrent,, tho- 
sometimes used with the ordinary sluice, is an indispensable 
part of the plant for hydraulic mining. The sluice is simple 
in construction and use, requires but little outlay of capital,, 
and is very effective. Unlike the outlays usually made in min¬ 
ing, the whole of the plant in use can be readily taken down 
and transported to another claim when the first is washed 
out, and set up there as effectively as if it were new. There 
is one precaution that must be taken with it, which is that 
lumps of clay must not be allowed to travel along it with¬ 
out being broken up, for they are liable to pick up the gold as 
they roll and carry it off with them. 

Getting the amalgam out of the sluice is called cleaning-up, 
and the time between one clean-up and another is called a run. 
The length of a run will depend on the richness of the deposit, 
but is usually from six days to two weeks, occasionally longer. 
A clean-up occupies about half a day, and is usually done on 
Sunday. To do this the water is allowe.d to run after the dirt 
is no longer thrown in, until it is quite clear; six or eight sets 
of riffle bars are then taken out at the head of the sluice, and 
the material washed down, while the amalgam is caught at the 
head of the next riffles. This is taken out. The next set of 
riffles are then taken out, and so on. The excess of mercury 
is strained from the amalgam by twisting it in a buckskin bag, 
and the rest is driven off by heat. 

HYDRAULIC MINING. 

For many years the sluice was used to work nearly the whole 
of the placer gold of the country, and it is still the most availa¬ 
ble way for persons of small capital to treat the shallow placer 
deposits. It must always be looked upon as a process of great 
historical interest, for out of it hydraulic mining grew, which 


THE METALLURGY OF GOLD AND SILVER. 15 


is one of the most marvellous achievements of modern engineer¬ 
ing skill, to which the State of California is more indebted than 
to all other inventions of mining and metallurgy put together 
There are localities where poor, shallow placers are found, where 
water is scarce during most of the year, but abundant at certain 
seasons, and where the grades are heavy. For these placers, 
another sluice was used, known as the ditch or ground sluice. 
A small ditch is cut through the placer and the water turned 
into it, the first object being to deepen and enlarge the ditch tO' 
the proper size. When this has been accomplished, the banks 
are pried into the stream. No mercury is used, but cobble¬ 
stones are thrown into the bottom of the ditch so that the 
gold may settle between them. The effort is to concentrate 
the gold in the dirt and then work it up in a short board sluice. 

These two methods put together were the germs of hydraulic 
mining now so extensively used in all parts of the world, not 
only for gold mining, but for the removal of dirt from other ores. 
It appears singular that the name of the man who really invented 
the most remarkable process of this century should be as lost to 
history as if he had never existed ; but in the struggle for exist¬ 
ence, as the shallow placers grew poorer and poorer, and the gold 
was found at constantly increasing depths, the man was lost 
sight of, while his work has now been so perfected that it is one 
of the marvels of the union of modern engineering skill with 
capital. The process of hydraulic mining was invented in the 
spring of the year 1852, on the Yankee Jim claim in Placer Co., 
California,^ where an enterprising miner, finding that he was not 
making sufficient money, began working his claim with a shallow 
ditch in the side of a hill leading to an ordinary barrel, from the 
bottom of which a cowhide hose was carried and discharged by 
means of a tin pipe against the bank, and he thus became the 
father of one of the greatest of modern inventions, hydraulic 
mining. 

There is another kind of placer which deserves notice, both 
because it is interesting in itself and because it has been the 
source of disappointment and loss to so many. This is the 
beach gold, which occurs between Point Mendocino in Northern 
California and the mouth of the Umpqua River in Southern 
Oregon. The cliffs along the ocean front seem to be the remains 
of an ancient river deposit. They contain gold, and where 


^ Engineeringy London, Eng., vol. 24, p. 353. 


i6 THE METALLURGY OE GOLD AND SLLVER, 


washed by the waves often show the shore for miles glittering 
with it. It is very uncertain, however, for what appears to-day 
is washed away to-morrow. No dependence can be placed on 
finding in the morning the deposit of the day before, so that all 
haste is made to carry the sands which are rich enough to some 
safe place inland to be washed and amalgamated. The beach is 
very narrow, and when the waves are high they wash against 
the bank. The gold is washed out with the heavy sand, and as 
the particles are very fine, it is carried down to near the low- 
water mark. When the ocean is still, sands of variable richness 
can be collected, but the waves are often so high as to wash all 
the sand away to the depth sometimes of six feet, and leave the 
bare rocks exposed. So changing and shifting is the value of 
the deposit that it has to be examined every day, and the wash¬ 
ing of the following day may sometimes be six miles from that 
of the previous one. Such sands as these must be very rich to 
make it possible to run the risk of washing them and to bear the 
transportation to fresh water, as salt water is of too high a spe¬ 
cific gravity to work with, for which reason the attempt to work 
these deposits by dredging has not been successful. It has been 
proposed to bring water from a distance and turn these mines 
into hydraulic placers washing down the banks, and depending 
on them for their profit, leaving the beach sands as an accessory. 
The tails would not then be a question of importance, but the 
economic results of such an enterprise would be very doubtful. 

After the introduction of sluicing either on a large or small 
scale, the pan, the cradle, and the rocker were very rapidly 
abandoned to John Chinaman, who always succeeded in living 
off the placers that had been abandoned by the “ honest miner,” 
who, however, never had any compunction, if he found the Chi¬ 
namen were tolerably prosperous, in jumping their claims and 
driving poor John off to find some other place for his enterprise 
and cheap labor. 

From hundreds of dollars a day, by a gradual decrease 
stretching over a period of from fifteen to twenty years, the gold 
became scarcer and scarcer, until now it has become necessary 
with improved appliances to work in the deep placers material 
which contains from 3 cents to $1.25 per cubic yard.^ 

’ In the spring of 1880 I was informed by the President of the North Bloom¬ 
field Mining Company that they were now working with a profit gravel containing 
only three cents to the cubic yard, when only a few years ago it was considered a 
marvel to be able to work that which yielded ten cents. 


THE METALLURGY OF GOLD AND SLLVER. 


17 


No better evidence of the progress that has been made in the 
working of placer claims can be had than the comparison of the 
cost of working them by the older and by the more recent pro¬ 
cesses. Adopting four dollars per day as the wages of a skilled 
miner, the cost of working a cubic yard of gravel as given by 
Phillips is— 

With the pan.$20 00 With the long Tom.00 

“ “ rocker. 5 00 “ “ hydraulic process. 02 

In the very early days the capital required by a miner con¬ 
sisted of a pick, shovel, a horn and spoon and a pan, two stout 
hands, and a valiant heart; but as the placer mines grew poorer 
this capital was no longer sufficient. It can readily be under¬ 
stood that such capital as was required in the early days did not 
necessitate any permanent location nor any very high order of 
intelligence for its use, and hence much of the surface was dug 
over and simply rendered difficult to work further without ex¬ 
tracting more than a tithe of the wealth contained in the ground, 
merely because the miner had no permanent interest in one spot 
more than another, and because his capital was entirely a rolling 
and not an invested one. Every man then was in business for 
himself, but as the gold grew scarcer, first money, and then intel¬ 
ligence and capital became factors in the equation, sq that the 
capital required to work any one of these claims became larger 
and larger, until to-day it is estimated that the plant of the 
North Bloomfield Mining Company has cost not less than 
$3,000,000, and their works are marvels both for the originality 
and engineering ability displayed, consisting of dams 90 to 100 
feet high, ditches, pipes, and sluices many miles in length, and 
every hydraulic appliance which engineering skill and capital can 
add to their works. 

These deep placers are the deposits formed in the beds of an¬ 
cient rivers which have since been so covered by recent accumula¬ 
tions, or cut across by modern valleys of erosion that without a 
careful survey no one could recognize table-lands twenty miles 
distant as part of the same ancient river deposit. In some cases 
the gold-bearing material has been covered by beds of basalt 
one hundred and fifty feet thick.^ In many cases the erosion 

* A map of the basalt-capped deposits of the North Bloomfield Co. is given irh 
the Report of the U. S. Mining Commissioner for 1875, p. 116. 







t8 the metallurgy OF GOLD AND SLLVER. 


has been such that the bed of the old river is now one hundred 
or even two hundred feet above the surrounding country. 

To work these deposits, careful surveys of the whole country 
must be made so as to be able to reach with a tunnel the lowest 
point of the bed-rock, which must be determined by sinking 
shafts upon it. The cost of this preliminary work may often be 
more than $100,000, and instances have been known where 
from want of proper judgment in the outset the whole of this 
sum has been lost. The location of the tunnel must be such 
that the pay dirt can be washed through it, and that it may 
form an outlet for all the material which is deposited after the 
extraction of the gold. Its construction involves the building 
of miles of sluices to catch the gold and carry the dirt away; 
the damming of streams to save the winter’s water supply; the 
storing up of billions of gallons, and conducting it in ditches, 
flumes, and wrought-iron pipes, sometimes forty, fifty, or even 
a hundred miles in length, the ditches alone costing in some 
cases from half a million to a million of dollars, and involving 
constructions which are marvels of lightness, strength, and en¬ 
gineering skill. The following table^ gives a fair idea of the size 
and cost of the ditches in California: 


Smartsville ditches. 

Eureka Lake and Yuba ditches... 
N.Bloomf’d ditches and reservoirs 

South Yuba ditches. 

Milton ditches and reservoirs..., 

Spring Valley and Cherokee. 

Hendricks. 

Blue Tent. 

La Grange. 


Leng^th 

Miles. 

Capaci¬ 
ty in 
Miner’s 
Inches. 

Grade. 
Feet 
per mile. 

Size in Feet. 

Cost. 

Top. 

Bot¬ 

tom. 

Depth 


5,000 

9 

8 

5 

4 

$1,000,000 

163 

5,800 





723.342 

157 

3,200 

12 to 16 

8i 

5 

3 i 

708,841 

123 

7,000 

3 to 13 

6 

• • • • 

4 to 5 


80 

3,000 

12 to 15 

6 

4 

3 ^ 

391.575 

52 

2,000 


5 




4 oi 


6 to 12 

5 

• • * « 

2 

136,150 

32 

18,000 

10 

8 

6 

4 

150,000 

20 

27,000 

7 to 8 

9 

6 

4 

500,000 


This water is discharged through iron nozzles with a velocity of 
one hundred and fifty feet per second, and at the rate, in some 
in.stances, of 4,220,000 cubic feet in twenty-four hours, against 
a bank from 250 to 300 feet high, and washes the earth into 
wooden sluices paved with rock or wood. To make the action 
of the water more effective, the bank is mined and fired, single 
blasts of from 1500 to 2000 kegs of powder being made. 

^ Burchard, “Production of Gold and Silver in the United States,” p. 318. 
Washington, i88i. 


































THE METALLURGY OF GOLD AND SLLVER. 


19 


As everything in the bank must come down, huge cranes 
with booms ninety feet long worked by hurdy-gurdy water¬ 
wheels are set up to lift the boulders,' under-currents’ to catch 
the gold, grislies’ to carry off the stones, drops" to break the 
materials up. The sluice itself has to be paved with stone or wood ‘ 
and furnished with branches, so that one part may be repaired 
without detriment to the other. Every part must work har¬ 
moniously with the other parts, and must be adapted to the 
lay of the ground, and every possible resource in the surround¬ 
ings made use of for its successful working. Individual enter¬ 
prise could do little or nothing with such claims, but the con¬ 
stant and large returns show that the immense outlay is fully 
justified. 

The gold is caught in mercury put into the sluices between 
the pavement and riffles. The greatest difficulty is not so much 
to catch the gold as to get rid of the tailings or material that 
has been treated. This involves the construction of miles of 
tail-sluices and the destruction of land and of streams by depos¬ 
iting on and in them stones and sand to great depths, but it 
saves for the use of the country the very large amounts of gold 
deposited in exceedingly small quantities in the ancient river¬ 
beds of California. No one who has not visited these mines*can 
have any idea of the devastation produced by this washing 
away of hundreds of acres of surface and hundreds of feet in 
depth of the ground of these gold-bearing districts. It will be 
many years before this question of local devastation will need to 
be considered, but the filling up of the rivers and streams is 
engaging attention now. 

The cost of producing one Troy ounce of metal is given 
below: ® 


La Grange Co. 


Water.‘.$i-43 

Labor.6.85 

Materials. 1.81 

Explosives . 

Blocks and lumber. 

General expenses.0.94 . 

Contingent expenses. 0.26 

Taxes. 0.09 


No. Bloomfield Co. 
$2.09 

3-93 

0.88 

0.98 

0.50 

0.70 


$11.38 $9.08 


^Engineering, vol. 25, p. 58. ^Engineering, vol. 24, p. 487. 

^Engineering, vol. 25, p. 20. ^ Ibid. ® Ibid. 

* The value of the metal was $18.53 per ounce. 












20 


20 THE METALLURGY OF 

GOLD AND 

SIL VER. 

The height of the bank washed 

down.and 

the 

yield for sev- 

eral mines is given below d 





Height of Bank Yield per Cubic Yard 
in Feet. in Cents. 

Smartsville Claims, Yuba Co. 

II2 

1 

19-5 

Blue Tent, Nevada Co. 

180 


15 

North Bloomfield, Nevada Co. 

.. 180 to 260 


4 to 6.5 

Gold Run, Placer Co. 

200 


4.8 

Columbia Hill, Milton Co . 

. . 100 


4.33 

La Grange, Stanislaus Co. 



2.5 to 15.5 

Patricksville, Stanislaus Co. 


L 

P33 to 18.5 

Dardanelles, Placer Co. 



13 

The cost and yield per cubic 

yard of some of the mines is 

given below 


Cost. 

Yield. 



$0.06 

$0.60 



0.03 

0.15 



0.025 

1 0.71 



0.02 

0.25 



0.02 

0.125 


The cowhide hose used at first soon became rotten and burst. 
This was succeeded by one made of heavy duck from four to ten 
inches in diameter. This was made sometimes of one, sometimes 
of two thicknesses. Such a hose will bear a pressure of fifty feet, 
but no more. To make it stronger it was surrounded by iron 
rings two inches wide and three inches apart, which were held 
in position by four ropes distributed evenly in the diameter. 
Such a pipe was called a crinoline hose, and would support a 
head of from 150 to 200 feet of water. This was subsequently 
abandoned for the sheet-iron pipe now generally in use. The 
profits of this kind of mining do not depend so much on the 
yield of the pay dirt as they do upon the cost of the water, 
the expense of getting rid of the tails, and the facility of work¬ 
ing which depends on the lay of the ground. A claim well 
situated can work a much poorer gravel with a profit than one 
less advantageously placed. 

TREATMENT OF GOLD QUARTZ. 

As the placers grew poorer and the search for other sources 
of gold became active, the prospectors soon found gold in veins, 

1 Burchard, “Production of Gold and Silver in the United States,” p. 318. 
Washington, 1881. 

2 Engineering, vol. 25, p. 59. 















THE METALLURGY OF GOLD AND SLLVER. 


21 


and these were then explored and worked. It was usually 
found in a hard rock which was ascertained to be quartz, but 
when it was afterwards discovered in other rocks no attention 
was paid to the correct name of the stone. The gangue of the 
gold was always called “ the quartz,” no matter how hard or 
how soft the rock was, or what its chemical composition might 
be; the “ quartz,” if it was quartz, was said to be hard, if it was 
slate it was said to be soft. To “ get” the vein rock required 
capital and a much higher degree of skill than had as yet been 
required for the working of the shallow placers. Deep quartz 
mining could not be carried on by individuals, and mining com¬ 
panies were formed to mine the quartz and separate the gold. 
At first these were all undoubtedly legitimate enterprises, but 
it was not long before some men found or thought they found 
a more expeditious road to wealth in mining shares than in 
mining quartz—a practice which very soon brought discredit 
on all kinds of enterprises in the State of California. 

To get the gold out of the vein-rock it had to be crushed. 
This was done in the very early days before mining companies 
were known, with a large rock bound to a pole supported on a 
crutch so as to have a long purchase. The rock was raised by 
one man and allowed to fall on the ore, while another kept the 
pieces of ore from flying away, with a stick of wood. It was not 
long before this rude Mexican hand labor was replaced by the 
arastra, which was a hearth or bed of uncut stones arranged in 
a circle from ten to twenty feet in diameter, with a curbing two 
feet deep on the inside, over which large stones were dragged 
by a single mule. It was necessary to run this machine for at 
least a week, and sometimes for two or even three times as long, 
to make it worth while to clean up. The joints between the 
stones were so open that the mercury and amalgam settled down 
between them so that the whole bed had to be dug up, the earth 
carefully collected and washed, and the hearth replaced before 
a new charge could be made. The hearth was then improved 
by making it of cut stones with very close-fitting joints laid 
in cement. To the upright part one arm or two arms at right 
angles to the diameter of the bed were placed, and to each end 
of the arms stones weighing from four hundred to five hun¬ 
dred pounds were attached by chains so that the forward end 
was about two inches above the hearth while the other end 
dragged on it. One mule was counted for each stone, so that 
there were one- or two-mule arastras. To make the charge for 


22 


THE METALLURGY OE GOLD AND SLLFER. 


an arastra ten feet in diameter, five hundred pounds of quartz 
broken by hand to the size of a pigeon’s egg was put in, and 
the mules driven for four or five hours. Water is introduced to 
make a paste of the consistency of cream, and then quicksilver 
is added and the mule driven for two hours more. The paste 
is now thinned with water, the mule driven slowly for half an 
hour, the mud is run off, and another charge introduced. Four 
charges can be made in twenty-four hours, but two are generally 
all that are made, so that half a ton per day is about the limit 
of capacity of a ten-foot arastra. The clean-ups are easily and 
frequently made, so that this machine is a much better one 
than the first, which was built for very rude work. 

It is quite easy to see from this description where the idea of 
pan amalgamation originated. It needs but a few mechanical 
appliances to be added to have the description of the pan as now 
used. The arastra is still a useful article, and as it costs next to 
nothing to erect, it may be used as a prospecting tool. The 
principle on which it is constructed is an excellent one, the 
grinding perfect. It gives a large percentage of the assay value, 
but is too slow for use where large quantities are to be treated. 

The Chilian mill was used about the same time, and consists 
of a circular bed like the arastra, but the ore is crushed by two 
large circular wheels made either of stone or of cast-iron, which 
roll around on their edges. The methods used are the same. 
The machine is more expensive than the arastra, and does not 
do its work any better. It was not long before the eager and 
impatient miner found that the capacity of the arastra and of 
the Chilian mill was not sufficient for the profit which he wished 
to get out of his ore, and he looked to some of the crushing 
machines used in Europe to increase the capacity of his mill, 
and at the same time his hoped-for profit. The stamp-mill 
seemed the only one likely to be of use, and this was adopted. 
There were then but few mines whose output would justify the 
erection of stamps, but where it would do so they were built. In 
other cases the miners were obliged to depend either on the 
stamps of some neighboring mine being sufficiently at leisure to 
do other work than their own, or to mills being erected inde¬ 
pendently of the mines to do whatever work was brought to 
them. To distinguish such mills from the others they were 
called “custom mills.” They work for everybody and at a fixed 
price, reserving the tails for themselves, which they usually take 
care should be rich. 


THE METALLURGY OF GOLD AND SLLVER, 23 


The lumbering German stamp with its wooden stems eight 
inches square, its complicated and cumbersome cam shaft, and 
its inefficient mortar, was first built. Then some Cornishmen 
suggested the idea of the Cornish stamp, which, with its rectan¬ 
gular iron stems but inefficient mortar, was quickly put up, and 
was for a short time such an improvement that it was con¬ 
sidered to be the ultima thule of. crushing. This gradually 
grew into the rotating California stamps and its adjunct the 
Blake’s crusher, with its increased capacity and much better 
mechanical appliances, which is now almost exclusively used in 
California. The stamp with its head weighs from 500 to looo 
pounds. Its capacity is, for very hard rock one and a half tons, 
and for very soft rock four tons, in twenty-four hours. The 
average will be about two tons. It is built in batteries of five 
stamps each, so that each battery may be counted for ten tons 
in twenty-four hours—a capacity which, considering the cost, is 
very limited. It is in universal use in California, where no 
other means of crushing has been able to compete with it. In 
other parts of the country it has grown into the Ball’s stamp,* 
a very large and heavy rotating stamp, in which the force of 
the blow is increased by the pressure of steam to such an ex¬ 
tent that a single machine with one stamp-head is capable of 
crushing one hundred and ten tons of the hardest rock in 
twenty-four hours, and thus a single machine becomes equal in 
effectiveness to a sixty-stamp mill, which is the size of some 
of the largest mills in the West. No investigation has yet 
been made to ascertain the comparative efficiency of the use of 
power in these two machines. The Cornish, California, and Ball 
stamp are working side by side on Lake Superior, and it is to 
be hoped that experiments to settle the question of efficiency 
will be made. There are several other crushing machines which 
have lately been introduced, but none of them have been fully 
tested, tho some of, them seem to be of great promise. 

But it was not sufficient to crush the rock, the whole bulk 
of the crushed material had to pass over or through mercury in 
order to extract the gold and silver; and the quantity of this 
rock was so large that it produced losses in mercury so great 
as seriously to diminish the profits. Amalgamated plates and 
some free mercury were placed in the mortar, but this, unless 

^ “ Stamp-Mills of California,” Enghteering, vol. 30, p. 19. 

* Aletallurgtcal Revieiv, vol. 2, p, 285. 


24 THE METALLURGY OF GOLD AND SLLVER. 


the pieces of gold were large, could never catch more than 
* eighty per cent of it, and when the pieces were small not 
more than seventy per cent. If the gold is associated with 
silver as in some of the Nevada mines, but very little of it is 
caught there, and the amalgam so produced is so light and 
spongy that it is liable to be carried off; so that where gold 
ores contain much silver, lead, or antimony, battery amalgama¬ 
tion is unadvisable. There are many g)ld-mills where it is 
never used, tho some of the best conducted ones do use it. 
There must therefore be a sluice at the end of the splash-box 
to catch the fine particles coming from the mortar. The 
sluice is thus, as an appendage to the battery, as important 
as the battery itself. It serves a very different purpose from 
the placer-sluice, where the dirt is to be transported, the clay 
broken up, and the stones carried along so as to allow the 
'gold to sink where the mercury is. The battery-sluice has 
neither to deal with stones, dirt, nor clay. It has to treat much 
less material ; it is therefore much shallower and has a lower 
grade. When- the ore contains copper and iron pyrites, these 
can by proper treatment be concentrated by it and saved. 
These battery-sluices are used with amalgamated copper plates 
with transverse riffles in which mercury is placed, and with the 
different kinds of blankets. Great attention is being given 
just now to *iron riffles, not only for battery but for placer 
sluices. The experiments made give reason to hope for a great 
saving of the precious metals by their use wherever sluices are 
used. In some localities the battery-sluice is used in connection 
with such machines as the Attwood’s amalgamator^ and the 
Eureka Rubber,^ but the tails are still rich. Some one suggested 
the use of cowhide with the hair on and the grain of the hair 
turned against the current, over which the tails were allowed to 
flow in order to catch the heavy materials, while the lighter 
ones were carried off by the stream ; and out of this grew all the 
different styles of stationary and revolving blanket-sluices. Still 
thetails showed by assay that they were rich, and it was then 
found that the gold was contained in iron pyrites. It is very 
remarkable that at this period when Mexicans with their arastras 
and slow but extremely simple processes could make $50 to $60 
a day, the best stamp-mills with the most efficient machinery, 
working on the same rock from the same vein could not recover 


^Engineerings, vol. 31, p. 247. 


* Ibid., p. 324. 


THE METALLURGY' OF GOLD AND SLLVER. 25 


from the ore more than $15 to $20. In some instances, with the 
best modern machinery an ore yielding by assay $700 to $800 
in gold did not yield more than $20 to $30 when stamped and 
treated with the usual appliances. The slower but more per¬ 
fect process of the arastra had brought the pyrites into such a 
fine state of division, and had by constant abrasion of the 
stone rubbed it so bright, that the “ quick” took it up, while 
the more rapid process of the stamp did not. As soon as it 
was thoroughly understood that the pyrites contained the gold, 
concentrators of different kinds, with or without buddies or 
keeves,^ were used to catch it, as no smelting process could be 
used in the localities where the pyrites was found, and the gold 
in the pyrites could not be separated with mercury. 

The tails are therefore generally kept to be put through a 
•series of concentrating machines whose object is to catch the 
pyrites and possibly some amalgam, but saves none of the gold 
which has escaped as float. It is a question of grave importance 
bow this gold may be caught, or, better, how to prevent its get¬ 
ting into the condition in which it cannot be caught. The miners 
call the gold that escapes the mercury “ float” and ‘‘ rusty” gold. 
That some gold exists in the ore in such fine particles that it will 
float seems undoubted; against this there is no remedy. It is 
also true that the heavy stamp falling on the ore does make float- 
;gold of some of the precious metal not in that state in the ore, 
but this is not the principal source of loss. If a piece of pure 
gold which amalgamates readily is pounded with a hammer on 
.a smooth anvil, it is very soon put into the condition in which 
mercury will not touch it.’ I have had such a piece of gold in 
contact with mercury for more than a week without amalgama¬ 
tion. From this condition the gold can readily be recovered in 
the laboratory, but it is doubtful if it can be saved in the mill. 
Something must be done to avoid it, as there seems to be no 
doubt that some part of the gold escapes amalgamation from this 
cause. But there is gold which is really rusty, not covered with 
a coating of oxide of gold, but of something which prevents 
contact with the mercury. Absolute contact is necessary to 
.amalgamation, and the thinnest film between the two will pre¬ 
vent it. One of these coatings is oxide of iron, which does not 
occur very often and is very easily removed by abrasion, and 

* Engineering, London, vol. 31, p. 404. 

» " Trans. Inst. Min. Engs., Feb. meeting, 1881. 


26 THE METALLURGY OF GOLD AND SLLVER. 


another is said to be silica; grease from the stamp, or which 
may be in the water used, will also produce it. I have shown 
also that a small amount of sulphuretted hydrogen or sulph- 
hydrate of ammonia will produce exactly the same effect, leav¬ 
ing an impalpable greasy film on the outside which prevents, 
the action of the mercury.- In other words, a dirty mill, water 
which is not .clean and not carefully protected from drainage,, 
will affect the gold. No one has until now thought it necessary' 
to call attention to this subject. 

I have elsewhere shown ^ that there are many other interest¬ 
ing facts relating to the metallurgy of gold which have escaped! 
observation. How far they may affect its extraction from the- 
ores is yet to be seen. It seems, however, certain that we are- 
creating some of the difficulties, and that some other machine 
than the stamp will have to be used for pulverizing gold ores.. 

The cost of the treatment of a gold ore, including the mining,, 
varies very much and depends on a great variety of circumstan¬ 
ces, such as the hardness of the rock, cost of transportation^, 
price of labor, etc. It may vary from one to ten dollars per ton.. 
It is usually higher in custom mills than in those mills owned by- 
the mine, where the quantity treated is very large. In such 
mills the cost of crushing, varying with the rock, will be from one- 
to two dollars per ton. In the custom mill where only a small' 
quantity is run it may be as high as five dollars for the same ore.. 
The yield of the ore and the consequent profits are very variable.. 
Ores yielding as low as five dollars have been treated in a large¬ 
way with a profit, but so much depends both on the nature of the- 
ore and on local circumstances, such as the management of the- 
mill, that it is quite impossible to say how poor an ore could be 
worked. Perhaps no one thing has been so great a stimulus, 
toward the perfection of the gold processes of California as the 
discovery of the mercury-mines there.^ The demand for a large 
quantity of mercury so stimulated the rival companies that they 
improved their process to cheapen their production, and found* 
themselves with such active competition that the price of quick¬ 
silver has fallen to less than one fourth of what it was, so that 
the free use of mercury is no longer feared in the poor mines, 
and the ominous question of the loss in mercury does not loom 
so high nor figure for so large a part of the cost in the processes^ 
as formerly. 

^ Trans. Inst. Min. Engs., Feb. meeting, i88i. 

’ Engineering, vol. 28, p. 239. 



THE METALLURGY OF GOLD AND SILVER. 27 

For a number of years all the metallurgical losses of gold¬ 
mining were attributed to sulphurets, and processes for working, 
these were invented without number, most of which have died‘ 
out long ago. The beautiful process of Plattner ^ for roasting; 
these sulphurets and then extracting the gold by chlorine was' 
adopted and improved upon, and for a long time seemed to have’ 
solved the question, but little by little it was ascertained that- 
there were certain substances contained in the gangue of the 
rock, such as lime and magnesia, and certain other substances- 
which might be associated with the gold, such as lead and zinc, 
which would be attacked by the chlorine, and that there were’ 
circumstances in which after the gold was in a soluble form in 
the tanks it might be again precipitated in the insoluble materiali 
of the ore, and thus be lost. Recent experiments have been* 
made with nascent chlorine with this gas under pressure, and 
other modifications which give promise for the future. It is 
apparent, however, that Plattner’s process in any or all of its- 
modifications does not cure all the evils, because it does not 
cover every variety of case, but is only applicable to certain* 
ores in which there is nothing but the gold in the ore which 
would be attacked by the chlorine, and nothing which would 
prevent its acting on the gold.’ 

If the ore contained any silver this would be attacked, and a’ 
coating of insoluble chloride of silver would be formed over the- 
gold ; this would prevent further attack by the gas, and not only 
would the silver be entirely lost, but any particles of gold con¬ 
tained in it would also be lost. A very careful dressing might 
separate some of the gangue attacked by the chloride, but it 
could never separate the whole, and any part of it remaining 
would be a source of loss ; so that as a general rule it may be’ 
stated that when the ore contains anything but gold which the 
chlorine will attack, the process - is not applicable. Besides,- 
Plattner’s process depends upon delicate chemical reactions.- 
If, for instance, any of the sulphate of iron resulting from 
the roasting is left in the ore, as soon as the gold has been put 
into a soluble condition and is leached with water, a part of 
the gold dissolved is thrown down by the sulphate of iron.- 
Certain organic compounds produce the same results. The’ 
gold thus previously rendered soluble is then precipitated in the 

' Engineering, London, vol. 24, p. 119. 

* Clay becomes diluted in the water. The earthy particles in suspension settle 
on the small flakes of gold and prevent the action of the chlorine. 


28 THE METALLURGY OE GOLD AND SLLVER. 


filter of gravel on the bottom of the tub and is lost/ I saw such 
an accident at Grass-Valley, and on examining the sand of the 
filter found it very rich in gold. It is not very wonderful, there¬ 
fore, that a process which demands such nice working and de¬ 
pends on exact chemical reactions does not succeed very well 
where there are no trained metallurgists. I have known an 
expensive plant abandoned and the process brought into great 
disrepute for one of the reasons given above, when if there had 
been a trained metallurgist in charge there is every probability 
that the defect would have been remedied and the process would 
have succeeded. 

It sometimes happens, too, that where the process is other¬ 
wise applicable, certain substances held in solution in the water 
of the district, if the gold already dissolved in the water is al¬ 
lowed to remain for a short time in the tanks, and sometimes 
by simply filtering through them, cause the gold already dis¬ 
solved to be precipitated on the filter and thus to be lost. In 
some cases where the works might have been successful had 
there been only one, there were so many competing for the pro- 
•duct of the district that they were obliged to lie idle more than 
half the time or pay a higher price for the concentrates than 
they were worth, in order to keep at work. 

As a result of the knowledge that gold could be recovered 
from the tails, there followed a series of concentrating-machines, 
•of blanket-sluices, of different kinds of amalgamators, of pans 
for grinding and amalgamating, and of single machines for doing 
.a dozen things which require to be done each by a separate 
machine in order to be well done. 

For a number of years the idea that gold and silver could be 
•concentrated by means of smelting had not occurred to the 
people in the West. The miner had divided his ores into placer 
.and milling ores, and the latter into free milling and rebellious, 
by which he meant ores which would or would not readily 
amalgamate. Such rebellious ores as would not yield to mercury 
.after working, or to which some leaching process was not ap¬ 
plicable, were treated for what could be got out of them. To 
make it possible to treat them by any other process to recover 
the gold, either copper or lead must be in such quantities that 
smelting will be remunerative. Such is usually the case to make 
.the treatment for gold alone possible. It occurs in Colorado, 


* Trans. Amer. Inst. Min. Engs.^ Feb. .1881. 


THE METALLURGY OF GOLD AND SLLVER. 29. 


where a complicated European process^ has been introduced 
with such modifications as were made necessary by local circum¬ 
stances to treat ores of copper or lead containing gold, to which 
all the rebellious ores of the district can be profitably added;, 
but the lead is always lost, while the copper is saved as a by¬ 
product. The gold thus concentrated in Colorado in a copper 
product is afterwards separated with little loss. If the gold is 
concentrated in a lead product, silver must be present, when the 
gold follows the silver and is afterwards separated from it. 

Such methods of smelting are not common. Gold is not 
usually found in the United States in paying quantities in cop¬ 
per or lead ores, nor have those ores as a general rule 
been found in any very large quantities in the districts where 
rebellious gold ores occur, nor if they did, could the separa¬ 
tion be undertaken except by men of great skill both in metal¬ 
lurgy and in financiering, as the failure of enterprises of this, 
kind based on either the one or the other, but without both,, 
has sho.wn. 

That gold associated with copper, lead, silver, and zinc 
could be separated by smelting when either lead or copper ore 
could be had in sufficient quantity, was learned after a long 
trial, but not until hundreds of thousands of tons of rich 
tailings from amalgamating processes, containing over four 
pounds of mercury to the ton in addition to large quantities, 
of gold and silver, had been allowed to run to waste in the 
streams which flow down the cafions of the mining districts. 

We cannot say that we have reached the utmost limit of 
metallurgical progress in the economical separation of the pre¬ 
cious metals, for it has been ascertained that in the hydraulic 
mines, from which by far the larger part of the gold of Cali¬ 
fornia is produced, notwithstanding the great cost of their plant, 
not more than thirty-three per cent of the total amount of gold 
contained is saved. 

The observer who takes the pains to calculate the millions of 
dollars contained in the tails which have been allowed to flow 
away looks aghast at these statistics, but the miner when he 
comes to consider them makes the very intelligent reply that 
while he gets out only thirty-three per cent he makes a profit 
for himself and his stockholders, but when he endeavors to save 
any portion of the other two thirds he makes either less profit 


^ Trans. Amer. Inst, Min, Engs., vol. 4 » PP* 285, 295. 


30 THE METALLUEGY OF GOLD AND SILVER. 


jor none at all, according to the amount of increase which he at¬ 
tempts to make. It is a matter of great regret to him that he 
.cannot save the sixty-six per cent, but his regret is not that it 
is wealth lost which would be added to the wealth of the State, 
but that he cannot have it at the bottom of his own pocket; so 
he abandons it philosophically to the future miner with the ex¬ 
pectation that nature will some time concentrate these tailings, 
-or that some process will be invented by which the vast value 
contained in the tailings that are now lying piled up in many of 
ihe cafions of the West can be utilized. In the mean time the 
filling up of the river-beds* and the covering of some of the 
agricultural lands have become a serious political question, and 
it may be that in the near future California, which would proba¬ 
bly not have been settled but by a mining population, will have 
to decide whether it will allow the agriculturist, who does not 
add nearly so much to the wealth of the State, to drive the 
.miner out of the deep placer districts where he settled long 
before the farmer came there, since the granger element threaten 
proscription in the shape of legislation which compels the miner 
to r.etain his tailings in the side canons and not to allow them 
‘.to escape into the rivers or over the arable lands. This ques¬ 
tion has recently come into the courts of California by an injunc¬ 
tion restraining the Miocene Mining Company of Butte Co. in 
that State, who own 1500 acres on Feather River of placers 
thirty feet deep, from discharging their tails into this river. 
The magnitude of the interests involved is shown by the follow¬ 
ing figures taken from the San Francisco Alta of June, 1881 : 


Miles of ditches and canals in the counties affected.. 6,000 

Number of men employed, from.5,000 to 10,000 

“ “ Chinamen. 500 

Capital invested in the mines. $150,000,000 

Yearly product. $12,000,000 to $15,000,000 

Mining population affected by the suit. 130,000 

Agricultural “ “ “ “ “ .' 60,000 


' The Tuolumne River in California was formerly five hundred feet wide and 
'fourteen feet deep in the bed of the river, and had a fall of eighteen feet to the 
mile. In twenty-one months it was filled so that the water hardly ran over the 
river-bed. In 1875-6 the freshets washed the river clear, but since then it has 
tbeen again filled, and is now only thirty-one feet wide and one foot deep. The 
Feather River fills up thirty feet in a single flood from these deposits, but scours 
itself free again, while the Yuba River at Marysville has filled permanently thirty 

feet, and fifteen miles above, one hundred and fifteen feet in thirty years._ Engin- 

.eering, London, vol. 25, p. 20. 








'THE METALLURGY OF GOLD AND SLLVER. '31 

It is estimated that should this injunction prevail the amount 
of farming land now under cultivation which will be rendered 
valueless by the removal of the mining population will be equal 
in money value to the total amount of the value of the mining 
property involved. Should this injunction be made permanent, 
the State will probably learn too late that a valuable industry 
;has been destroyed by people who found the mines working 
when they settled on the lands they occupy, and must have 
'known beforehand what was in store for them in the near future. 
The industry so destroyed it will be difficult to re-establish, and 
:it is very doubtful whether the State will be a gainer by it. 

TREATMENT OF SILVER ORES. 

* 

As gold grew scarcer silver ores were looked for and became 
an object of great interest. At first only the rich outcrops of 
the free-milling lodes were worked, and the ores from them were 
treated by the old Patio processes which were found in Mexico, 
in which arastras and Chilian mills were used. Occasionally 
the Caso method was adopted by some person who had seen it 
at work or had heard of its working in Chili. The Caso method, 
working quicker than the Patio, was adopted in some places; 
•the bottom of the box was replaced by iron, and then the sides, 
,and then the idea of grinding suggested itself, until the amalga¬ 
mation pan in all its varieties grew up little by little. It was at 
first thought that the pan could be used equally well for both 
'grinding and amalgamating, and some persons still use it for both 
purposes. But it has been pretty well settled of late years that 
the machine can do only one kind of work well, and that any 
'Other kind of work forced from it is done at the expense of the 
yield. 

The Freiberg barrel did not meet with much favor in the 
West. Most of the emigrants of 1848 were of Anglo-Saxon ori- 
;gin, and when the German came with his slow but certain meth¬ 
ods, a few mills adopted the barrel. But in the early days quick 
returns were demanded. The pan was an American invention. 
It moreover had grown on “the coast,” ‘ and every one knew or 
thought he knew how to use it. Every machine-shop was ready 
to make it, and was more or less interested in one of the many 
-patents taken out for a new one. It gave a return in from three 
ito five hours, while the barrel worked twenty-four before the 

^ All the Sierra Nevada district is called “the coast" in the West. 


32 THE METALLURGY OF GOLD AND SILVER, 


amalgam was extracted. The pan required nothing but the ore^ 
mercury, “the chemicals,’' and water. These had to be used in 
the barrels, and in addition some iron. Balls were used at first 
as in Europe, then pieces cut from stamp stems, and then mule 
and horse shoes, and finally anything made of iron whether 
adapted by its shape to the purpose or not. The result was im¬ 
perfect, partly from the want of material adapted to the pur¬ 
pose, and partly because it was not always possible to get the 
material wanted in a given time. The consequence was that 
most of the mills that put up barrels found no one to run them,, 
or were obliged to keep one set of men to run and another to 
repair them. Yankee wit did improve them so as to make 
each barrel independent by using friction clutches, and by doing 
away with the cogging by the substitution of friction gear; but 
a change in the administration usually threw the barrels out and 
put in the pans, so that the barrel, while everywhere condemned 
in favor of the pan, has really not been fairly tested. It is- 
cheaper to erect and cheaper to run, but slower in action, and 
with friction gear ought to compete with the pan. 

Amalgamation whether in the barrel or the pan was first 
used only for ores that are now called free-milling—that is, 
which will amalgamate immediately with the mercury. But 
it became evident soon that there was a large amount of 
ore which would not amalgamate. It contained sulphur and 
other substances which either prevented the action of the mer¬ 
cury altogether or caused a great loss of it. Such ores were 
called rebellious, and at first were not used ; afterward they 
were roasted, the principal object of the roasting being not only 
to drive off the sulphur which was present, but by adding a little 
salt to convert the silver into chlorides which could be easily 
attacked by the mercury, which process was called the Reese 
River Process in distinction from the Washoe, which is the free- 
milling. 

Up to this time stamping had generally been done wet in 
order to avoid the losses occasioned by the dust, as there was 
no reason why in the Washoe process the wet ore should not be 
delivered to the pans as soon as it settled sufficiently to form 
the “ pulp,” but with rebellious ores in regions where fuel was 
generally scarce, too much heat would have to be used in driv¬ 
ing out the moisture from the ore,^ and dry-stamping took the 

^ “ The Stamp Mills of California,” Engineering-,'London, Eng., vol. 31, p. 246. 


THE METALLURGY OF GOLD AND SLLVER. 


33 


place of the wet. As the ore came from the mine damp, drying 
floors, made by running the flues of the roasting furnace back¬ 
wards and forwards under the iron plates covering the floors 
behind the stamps, were used, and the ore from the mine was 
spread out over these plates until it was dry. As there was 
nothing but the force of the blow from the stamp-head to deliver 
the ore from the screens, the operation was slower, and as no 
wat6r current carried the ore away from the front of the stamps, 
endless chains were placed in the dust-tight boxes which enclosed 
the front of the mortar-screens, which delivered the crushed ore 
into bins in the roof of the works, whence it was delivered 
by spouts into the furnace. 

Every kind of furnace for roasting was invented and tried. 
These were usually some kind of reverberatory furnace, and were 
the subject of a large number of patents, and were altered and 
modified with more or less permanent success. Attempts 
were made to (nake the work wholly mechanical by the use of 
revolving cylinders into which the ore and salt were charged 
by machinery, in order to get rid of the difficult hand labor re¬ 
quired, and the necessary exposure to fumes in roasting in ordi¬ 
nary reverberatory furnaces. A few of these survive in the 
Bruckner^ and Teates furnaces, but as a general thing the cost 
of repairs to these contrivances, and the necessity of more 
enginerpower or of separate engines in the absence of machine- 
shops near at hand, increased the expense of working beyond 
the gain in diminished labor. 

On account of the large loss both in mercury and in silver 
which are carried off in the tails, mills ^ called tail-mills have 
been erected, where, notwithstanding the large loss in mercury 
which is known to exist in the treatment, there is a constant 
increase in the quantity of mercury, and very often a large yield 
in silver. These mills have no work to do unless the tails are 
accumulated by damming the valleys through which the tail- 
streams pass. When the accumulated tails have been treated, 
the mills have no further use, and very often the heavy freshets 
do the work first by sweeping the tails away. Sluices of great 
length and width have been put up, but their tails are still rich.® 
Many machines have been invented for catching mercury and 
amalgam by making the tails pass over revolving blankets, rub- 

^ Engineering, vol. 22, p. 575. 

’ “Treatment of Tailings,” Engineering, vol. 30, p. 395. 

^ Engineering, vol. 30, p, 395. ^ 


34 the metallurgy OF GOLD AND SLLVER. 


bers, revolving amalgamated plates, and many other contrivances, 
but they are not as yet successful in the commercial sense. 

When lead, copper, or zinc were present in the ores in any 
considerable quantity they became so rebellious that amalgama¬ 
tion was out of the question, and smelting, with its necessary 
adjunct of concentration, became necessary. As the dressed 
ores were rich and contained a large product condensed into a 
small one, and as this product was usually sold, sampling^ works 
sprung up, in which the value of a large quantity of ore was 
carefully ascertained by processes more or less mechanical, in 
which, as rapidity of execution as well as correctness of results 
were necessary, a number of tools for reducing the ore to pow¬ 
der now generally used were invented.® 

The first attempts at smelting, as they were usually con¬ 
ducted by persons of no great experience, were not very suc¬ 
cessful. In fact, the early history of the now very successful 
American methods is a record of failures. When the smelting 
of silver ores became a necessity, English methods were first 
introduced by the Cornish miners, only a few of the German and 
Swedish furnaces being used. But as the English type of fur¬ 
nace requires a considerable amount of good fuel, of a kind not 
generally found in the West, and the use of wood in them re¬ 
quires great skill, shaft furnaces gradually took their place, for 
the most part for treating ores containing gold, copper, silver, 
and lead by smelting.® Some of the processes adopted from 
the old works in Europe found themselves in circumstances 
where the conditions of transportation, labor, or fuel were such 
that they could not compete with other districts, so that they 
gradually disappeared, and were succeeded by the same pro¬ 
cesses in a new dress or in a new phase to such an extent that 
the plant and the process as it is now used in the West would 
hardly be recognized by their inventors. Little by little it was 
ascertained that when the ore contained any volatile material, 
although it might be in small quantities, it would carry off with 
it very considerable portions of the precious metal; and then 

arose the idea of condensing chambers, until gradually, without 
any one person having invented them, the methods have grown 

into the simple and very beautiful processes which are now in 
use in the West. 

^ Engineering, vol. 22, p. 495. 

^ Engineering, vol. 22, p. 495, figs. 5 to 12. 

^ Transactions of the American Institute of Mining Engineers, vol. 4, p. 275. 


THE METALLURGY OF GOLD AND SILVER, 35 


At first the only fuel used was charcoal, and this, as wood 
was scarce, was sometimes made from dead or from float wood,- 
or from woods too light for the purpose, so that it very often 
happened that the charcoal would crush by its own weight, and 
would not stand a charge in the furnace at all. It then became 
evident that the ores must have a comparatively high yield, and 
that as they usually had a gangue composed for the most part 
of silica, coke was necessary, and this, with from ten to twenty 
per cent of ash,^ was imported from the East or from Europe at 
an expense in some of the works of forty dollars a ton. As it 
became evident that coke was the necessary fuel, it also became 
apparent that something must be done to reduce its cost, and 
also the cost of the refractory materials. Water-back furnaces 
were then introduced, which consisted of cast or sheet iron boxes 
riveted together, surrounding the hottest part or the whole of 
the furnace and cooled with water. These furnaces were for the 
most part open-breast furnaces with front hearths, and were 
continually getting out of order from the formation of sows and 
bears which occasionally stuck to the bottom or formed engorge¬ 
ments in the furnace higher up. To avoid these the Ahrent’s 
tap was invented, which keeps a very considerable quantity of 
lead on the hearth of the furnace at all times, and allows of the 
casting being done without interfering with the interior. In other 
works where copper is in large quantity the ores are smelted 
for copper, and the silver and gold concentrated in one of the 
products, from which it is separated in the wet way by the 
skilful adaptation of old processes.^ 

It now became evident that there were considerable mechan¬ 
ical losses from the metal being carried up and out of the chim¬ 
ney, so that in some instances in Utah as much as ten or even 
fifteen or twenty per cent was carried off in this way. Attempts 
were then made to collect this material as is done in Europe in 
condensation chambers of large size and extent, and several sys¬ 
tems of doing it have been invented. The simplest, the cheap¬ 
est, and the most recent of these is used at Mansfield Valley, 
near Pittsburgh, Pennsylvania,® and is an adaptation of the flue 
leading to the chimney by dividing it in two sections vertically. 
In the lower one of these, partitions eighteen inches high, placed 

^ The high percentage of ash in the coke has in several instances caused the 
failure of works which with a suitable fuel might have been successful. 

® Trans. Amer. Inst. Min. Engs., vol. 4 > P- 276. 

2 Annals N. Y. Acad. Sci., vol. 2, p. 106. 


36 THE METALLURGY OF GOLD AND SLLVER. 


four or five feet apart and one third of the height of the flue, 
catch the dust by gravity, and as there is no velocity below, it 
remains there. The gas circulates above. 

Generally the silver and the gold in a district where lead ores 
can be had, are concentrated in a pig lead improperly called 
“ base bullion.” In some few cases fn the early days the Ger¬ 
man method of cupellation was used, but as this requires a 
maximum consumption of fuel, great skill, and a market for 
litharge, it was quickly superseded by the English method, 
which requires less skill, makes no litharge for sale, but re¬ 
quired the poor lead to be concentrated into a rich one and 
that treated for .gold and silver. The Patterson process by crys¬ 
tallization for enriching the lead previous to cupellation was 
never extensively used here, principally because at the time 
when there was a large amount of work to be done the process 
had already been superseded. The lead directly from the fur¬ 
nace is now enriched by zinc desilverization,* and the rich lead 
•cupelled in an English furnace. 

The history of this process is very peculiar. Invented in 
1842 by Karsten, it was declared a failure after, a prolonged 
investigation by that very able metallurgist. It was reinvented 
by Crooks in 1858 in England, where it was not very successful, 
and was brought to this country as an English process. It was 
tried again at Tarnowitz, in Silesia, and was more or less of a 
failure there, and was then reintroduced into this country, and 
so many improvements made in it that to-day the American 
modification of it has become the perfection of a process, and 
the furnace used a type furnace. 

In order to use the method of desilverization by zinc it is 
necessary that the lead should be very pure. To purify the 
lead small refining furnaces were used in Germany, containing 
.two to three, and subsequently from five to six, tons each. 
Eut in this country one of the first improvements made was 
the softening or purification of the lead in a furnace con¬ 
taining from fifteen to twenty, and subsequently as high as 
twenty-six tons; but as the hearth of such a furnace was diffi¬ 
cult of construction, it was simply made in a cast or wrought 
iron pan. This softened lead had to be discharged from the 
furnace, which was not an easy matter, and the late Mr. Steitz 


^ Annals N. Y. Acad. Sci., vol. 2, p. 86. 


THE METALLURGY OF GOLD AND SLLVER. 37 

invented a siphon ^ to do it, which seemed to be the perfec¬ 
tion of an instrument for this purpose. 

The refined lead is stirred with zinc, the zinc-scums carrjdng 
the silver with them are liquated to separate the excess of lead, 
and the result is a vei*}" rich zinc alloy, containing a large amount 
of lead, which is granulated and distilled in retorts. The distil¬ 
lation in retorts promised at one time to wreck the process, as it 
had to be effected in small furnaces^ surrounded by coke, and 
the number of retorts broken was large, notwithstanding the 
use of Steitz’s siphon. Petroleum was then tried with great 
success lessening the breakage of the retorts due to the charging 
of the fuel and the poking of the fire. Subsequently Mr. Faber 
du Faur invented his tilting furnace, which allows of pouring 
the rich silver lead out of the retort without disturbing it, thus 
removing all the difficulty. The silver, lead from which the zinc 
has been distilled is cupelled in an English furnace and cast 
into pigs. The lead from which the silver has been removed is 
refined in a furnace similar to the softening furnace, called a 
calciner. All the lead so refined is of the highest quality fit for 
the manufacture of white lead. It is produced almost as a by¬ 
product, and at a low cost. 

The improvements in cupellation have been, first, the in¬ 
vention of the iron cupel surrounded by water, by the late Mr. 
Steitz, of St. Louis, upon which the lead could be brought up 
to fine silver, and the later invention of IMr. Eurich, of the 
Pennsylvania Lead Company, of going from the lead riches to 
silver 996 fine, on a hearth made of Portland cement, and casting 
directly from the cupel into silver bricks by a simple arrangement 
for tipping the cupel.® - 

It sometimes happens that silver can be extracted from its 
ore in the wet way. There are three principal methods which 
have been used for this purpose.' The first was introduced in 
1849 t>y a German named Augustine, and consists^ in trans¬ 
forming the ore into chloride by roasting the ore to drive off 
the sulphur and other impurities, grinding the roasted ore and 
then roasting with salt to form chlorides; then dissolving out 
the chlorides with a saturated solution of salt, precipitating the 
silver with copper, compressing and melting the silver. It is 

^ Annals N. V. Acad. Sci., vol. 2, plate 7, fig. 6 ; plate 9, fig. 10. 

« Ibid., p. 9S. 3 Ibid., p. 108. 

^ Trans, Amer. Inst. Min. Engs., vol. 4, p. 295. 


38 THE METALLURGY OF GOLD AND SLLVER. 


usual to concentrate the silver into copper mattes for this pro¬ 
cess. Shortly after the invention of this process, another, much 
simpler, was invented by ZiervogeV which consists in roasting 
mattes to produce sulphates, decomposing all these sulphates 
except that of silver, and then dissolving out the sulphate of 
silver with hot water. Simple as it appears, this process is exceed¬ 
ingly difficult to execute, for it requires a very high degree of 
skill to seize the exact moment when all the sulphates of the 
other metals are decomposed and none of the silver is. If the 
sulphates are not all decomposed the silver is precipitated by 
them; if they are, there is danger that the silver sulphate also 
will be decomposed, and it will then be lost, as the oxide is not 
soluble. The practice, therefore, is to leave a little of the sul¬ 
phates of these metals undecomposed, as the loss in this case 
can be calculated beforehand, while no one can tell what it will 
be in the case of too much roasting. As these residues are 
always rich, they are often treated by the Augustine process, the 
two being very advantageously used together in this country.^ 

In looking at the silver process as a whole and comparing 
the cost, we find that the relations between the relative cost and 
quantity of silver extracted were very interesting. 



Relative 

Relative 


Cost. 

Loss. 

Amalgamation. 


2.0 

Augustine process. 


2.0 

Ziervogel “ . 


1,0 


The Ziervogel process is, both as to cost and residues, twice 
as advantageous as the others. 

Still another process was invented in 1858 by an Austrian of 
the name of Von Patera, which consists in roasting, as in the 
Augustine process, leaching with hot water before roasting with 
salt in order to dissolve out any soluble salts, roasting with salt, 
then dissolving the chlorides with hyposulphite of soda, precipi¬ 
tating the silver with polysulphite of sodium, and then reducing 
the sulphide of silver. This process is easily carried out, in that 
the reagents can readily be had, and that none of them are 
wasted; but both the lixiviation and the precipitation require 
such nice distinctions and such an exact chemical knowledge 
that it has not been very successful. 

The bullion which is produced as the result of treatment 
of any of the ores usually contains some small quantity of the 

^ Trans. Amer. Inst. Min. Engs., vol. 4, p. 245, 


Ibid., p. 295. 





THE METALLURGY OF GOLD AND SLLVER. 


39 


base metals besides the gold and silver. The gold from Cali¬ 
fornia generally contains about twelve per cent of silver, that 
from Australia four to six per cent. The amount varies from 
three per cent to about twenty-five per cent. The silver bullion 
often contains gold, as in the case of the Comstock, where 
one third of its value is gold ; and these metals must be sepa¬ 
rated in order that they may be alloyed to their proper stand¬ 
ards for commercial uses. Neither pure gold nor pure silver 
is of any use commercially except for electroplating; for all 
other purposes they would be much too soft. The process of 
separation is called parting. To effect this an alloy is made 
by melting, which usually contains three parts of silver to one 
of gold. In a single instance in California this alloy is three 
of silver to two of gold. The formation of this alloy is called 
quartation or inquartation. It is granulated and subjected 
to one of three different processes; the silver is dissolved out 
by either nitric or sulphuric acid, and in both cases the 
residue not dissolved will be gold. The nitrate of silver 
siphoned off from this is diluted with water and precipitated 
with salt. The chloride of silver so formed is reduced to a 
metallic state with sulphuric acid and zinc, and the silver melted 
into bars whose fineness is stamped on them, and they are then 
used for commercial purposes. In the case of sulphuric acid, 
sulphate of silver is formed, which is diluted with hot water and 
precipitated as metallic silver by copper. The spongy silver is 
pressed into cakes by a hydraulic press and melted into bars. 
The gold is collected, melted, and run into bars. The nitric 
acid method has been generally abandoned, because it poisons 
the neighborhood with fumes. The sulphuric-acid process, which 
is a little cheaper, has taken its place, except in California, where 
a very beautiful method, invented by Mr. Gutzkow,^ has taken 
its place. This method, which is very ingenious, much quicker . 
and gives better results than the others, was introduced in San 
Francisco in 1867. Most of the alloys are not granulated; they 
are inquartated and dissolved in sulphuric acid, in bars. The 
sulphate of silver is crystallized and a solution of sulphate of 
protoxide of iron run through it, which reduces the silver to a 
metallic state; the iron solution becomes sulphate of sesquiox- 
ide of iron, and is restored to its original condition with fresh 
iron and used again. The silver is pressed and melted as before. 


^ Burchard, “Production of Gold and Silver.’ Washington, 1881, p. 356. 


40 


THE METALLURGY OF GOLD AND SILVER. 

and the gold from the pots treated in the same way. This pro¬ 
cess is not only very simple, but is in a chemical way one of the 

f 

most beautiful known. 

The amount of silver produced in the United States previous 
to 1858 was so insignificant that no statistics have been re¬ 
corded. In that year it was only $500,000; in 1859 was only 
$100,000; in i860 it was $150,000; but in the following year, 
1861, the amount of silver began gradually to increase, until the 
year 1870, when it was $16,000,000. The total amount produced 
in this decade from i860 to 1870 was $*84,300,000, the lowest 
amount being $150,000, in i860. From 1870 to 1880 the amo'unt 
of silver becomes a very considerable factor in the world’s pro¬ 
duction of this metal, the highest amount being a little over 
$45,000,000, in 1878, and the lowest $i6,000,000, in 1870, the total 
production for the decade being $374,922,260. If these amounts 
of silver are added to the amounts of gold shown in the table, 
in the last number of the QUARTERLY, p. 80, it will be seen that 
for the decade from i860 to 1870, the highest production of 
precious metals was in 1869, $61,500,000, and the lowest was 
$43,700,000, in 1862, the total being $555,150,000. For the 
next decade, from 1870 to 1880, the highest production*was in 
the year 1878, $96,487,745, and Ihe lowest $66,000,000, in 1878. 
The largest amount of silver produced by any one State during 
the year 1880 was $17,000,000, obtained in Colorado, and the 
next largest $10,000,000, from Nevada. 


Year. 

Silver. 

Total Gold 
and Silver. 

1858. 

$500,000 

$50,500,000 

1859 . 

100,000 

50,100,000 

i860. 

150,000 

46,150,000 

1861. 

2,000,000 

45,000,000 

1862. 

4,500,000 

43,700,000 

1863. 

8,500,000 

48,500,000 

1864. 

11,000,000 

57,100,000 

1865. 

11,250,000 

64,475,000 

1866. 

10,000,000 

63,500,000 

1867. 

13,500,000 

65,225,000 

1868. 

12,000,000 

60,000,000 

1869. 

12,000,000 

61,500,000 


Year. 

Silver. 

Total Gold 
and Silver. 

1870. 

$16,000,000 

$ 66 , 000,000 

1871. 

23,000,000 

66,500,000 

1872.... 

28,750,000 

64,750,000 

1873 . 

35,750,000 

71,750.000 

1874 . 

37,324,594 

70,815,496 

1875 . 

31,727,560 

65,195,416 

1876. 

38,783,016 

78,712,182 

T877 . 

39,793,573 

86,690,963 

1878. 

45,281,385 

96,487,745 

1879 . 

40,812,132 

79,711,990 

1880. 

37,700,000 

73,700,000 


Such enormous productions of the precious metals have not 
been without their influence on the relative value of gold and 
silver in other countries. The United States is one of the larg-est 
producers of the precious metals, notwithstanding, as the statis- 







































THE METALLURGY OF GOLD AND SILVER. 41 

tics show, there has been a gradual falling off in the production 
of gold, and the highest limit of silver appears to have been in 
the year 1878, since which time the decrease in the production 
of the Comstock has brought down the production of silver 
from its maximum in 1878, nearly $8,000,ocx), and it seems likely 
that this decrease will continue. 

The amount of gold consumed in the United States for 
purposes of art and ornament during the year 1880 was larger 
than for several previous years. The following table from the 
Report of the Director of the Mint, which is a mine of informa¬ 
tion for those interested in the production and distribution of 
the precious metals, gives the returns of the New York Assay 
Office for that year: 


Bars Manufactured^ 



Gold. 

Silver. 

Total. 

From United States coin (defaced). 

Foreign coin. 

$4,929 

260,222 

1,007,400 

2,988,422 

394,871 

$98^ 

72,668 

278,622 

3,863,126 

144,992 

$5,911 

332,890 

1,286,022 

6,851,548 

539,863 

“ bullion... 

Domestic “ .. 

Plate, etc. 

Total. 

$4,655,844 

$4,360,390 

$9,016,234 



From the whole United States this amount is much larger; 
but leaving out the foreign bullion altogether, the following table 
gives the estimate of the total gold and silver used in the whole 
United States for industrial purposes during the last year: 



Silver. 

Gold. 

Domestic bullion. 

$4,000,000 

600,000 

400,000 

$5,000,000 

2,500,000 

2,500,000 

U. S. coin. 

Plate, foreign bullion, and coin. 


Amount consumed.. 

$5,000,000 

$10,000,000 


The consumption of the precious metals for purposes of 
art and ornament has been the subject of estimates by many 
distinguished statisticians, but at the best can only be approxi¬ 
mated. In 1827 Humboldt placed it at 375,000 ounces, or one 
•fifth of the world’s production at that time. In 1822 Lowe es¬ 
timated it at two thirds. William Jacob estimated it at 988,000 


^ Report Director of the Mint, 1880, p. 19. 






































42 


THE METALLURGY OF GOLD AND SLLVER. 


ounces, which was double the average annual production be¬ 
tween 1821 and 1830. Dr. Soetbeer, of Germany, gives the fol¬ 
lowing tables of the consumption of the precious metals for 
jewelry and other industrial purposes in the various countries of 
the world: ^ 

Gold. 



Consumption, 
in Ounces, 

Reduction by 
Old Material 
used. 

Total 

Consumption. 

United States. 

529,000 

10 per cent 

476,000 

Great Britain. 

703,000 

15 

598,000 

France. 

739,000 

20 “ 

591,000 

Germany. 

518,000 

20 “ 

412,000 

Switzerland. 

529,000 

25 

397,000 

Austria. 

102,000 

15 

87,000 

Italy. 

212,000 

25 

159,000 

Russia... 

106,000 

20 “ 

85,000 ■ . 

Other Countries.. 

176,000 

20 “ 

141,000 

Total. 

3,614,000 


2,946,000 


Silver. 



Consumption, 
in Ounces. 

Reduction by 
Old Material 
used. 

Total 

Consumption. 

United States. 

4,233,000 

15 per cent 

3,789,000 

Great Britain. 

3,175,000 

20 “ 

2,540,000 

France... 

3,528,000 

25 

2,646,000 

Austria-Hungary. 

1,411,000 

20 “ 

1,129,000 

Switzerland. 

1,129,000 

25 

847,000 

Italy. 

882,000 

25 

662,000 

Russia. 

1,411,000 

20 “ 

1,129,000 

Germany. 

3,528,000 

25 “ 

2,646,000 

Prussia. 

1,870,000 


1,411,000 

Total. 

21,167,000 


16,799,000 


Other estimates give the entire consumption of the precious 
metals in Europe and America for industrial purposes in 1880 
as from $45,000,000 to $55,000,000 in gold, and from $25,000,000 
to $30,000,000 in silver. 

From 1831 to 1880 the estimated consumption of gold for 
industrial purposes was 73,000,000 ounces, or 32.6 per cent of 
that produced. For silver it was 511,000,000, or 25.2 per cent. 

Of the world’s product of bullion it is estimated that one 
third is used up and lost in the wear and tear of coins and arti¬ 
cles made for use or ornament, one third is used for manufac¬ 
turing purposes, and one third goes to supply the increased de- 


^ Engineering and Mining Journal, vol. 32, p. 183. 



















































THE METALLURGY OF GOLD AND SLLVER. 


43 


Tnands of trade. The amount lost by the abrasion of coins is 
5 hown by the fact that the average life of an English sovereign 
is eighteen years, by which time the coin has lost three quarters 
of a grain and is no longer legal tender. Dr. Soetbeer^ states 
that the annual loss from this source in civilized countries 
reaches 28,000 ounces of gold and 1,600,000 ounces of silver. 

The following table “ shows the amount of gold and silver 
produced in the world in the years 1877, 1878 and 1879: 



1877. 

M 

00 

00 

1879. 

Gold. 

Silver. 

Gold. 

Silver. 

Gold. 

Silver. 

United States. 

Russia. 

Australia. 

$47,897,390 

27,226,668 

29,018,223 

996,898 

204,697 

1,196,278 

2,658 

$ 39 , 793,573 

467,844 

$51,206,360 

27,967,697 

29,018,223 

996,898 

205,361 

1,196,278 

6,001 

$45,281,385 

448,016 

$38,899,858 

26,584,000 

29,018,223 

989,161 

205,361 

1,062,031 

1,994 

$40,812,132 

415,676 

Mexico. 

Germany. 

Austria. 

Sweden. 

Norway. 

27,018,980 

6,135,877 

2,119,948 

54,038 

188,052 

17,949 

2,078,380 

420,225 

1,000,000 

1,039,190 

706,649 

27,018,940 

6,938,073 

2,161,515 

52,708 

166,270 

17,949 

2,078,380 

420,225 

1,000,000 

1,039,190 

728,846 

25,167,763 

6,938,073 

2,002,727 

62,435 

166,270 

17,949 

2,078,380 

420,225 

1,000,000 

1,039,190 

916,400 

Italy.. 

Rest of Europe. 

72,375 

72,375 

72,375 

Argentine Republic.. 

Colombia. 

Rest of S. America... 

Japan. 

Africa. 

78,546 

4,000,000 

1,993,800 

265,840 

1,993,800 

78,546 

4,000,000 

1,993,800 

295,746 

1,993,800 

78,546 

4,000,000 

1,993,800 

466,548 

1,993,800 

Total.. 




$113,947,173 

$81,040,665! $119,031, o85’ $87,351,497 

$105,365,697! $81,031,220 


Dr. Soetbeer® gives the totals as: 

1877. 1878. 1879. 

Gold. Silver. Gold. Silver. Gold. Silver. 

■$121,514,026 $96,855,376 $122,058,368 $104,126,608 $104,245,987 $102,229,521 

These tables show that the United States is by far the great¬ 
est producer of the precious metals, Russia being the only one 
which produces anything like as much gold, and Mexico the 
only one that approaches it in silver. 

The amount of precious'‘ metals sent to the East, the greater 
part of which goes to India, has been estimated by Dr. Soet- 


beeras: 

Gold, in Ounces. Si.ver, in Ounces. 

1831-1840. 35,000 7,750,000 

1871-1880. 423,000 38,000,000 

1831-1880..*. 19,700,000 1,376,000,000 


In the period from 1871-1880, which is most reliable, the 
consumption of gold by this means was 47,000 ounces, and of 

^ Engineering and Mining Journal, vol. 32, p. 182. 

2 Report Director of the U. S. Mint, 1880, p. 159. 

^ Engineering and Mining Journal, vol. 32, P* 182. Ibid., p. 183. 






















































44 the metallurgy OF GOLD AND SLLVER. 


silver 4,200,000 ounces. In India alone the imports in the last 
forty years have exceeded the exports of these metals by $400,- 
000,000, of which only $8,000,000 have been coined as money. 

The amount of the precious metals hoarded or put out of 
circulation either as objects of art or ornament is becoming 
greater with every decade. It appears from the data given 
page 167 that the total annual consumption of the precious 
metals for purposes other than coinage is about 3,600,000 
ounces of gold and 21,000,000 of silver. It has been estimated 
that the entire amount of gold now in the world is only equal 
to that which has been produced in the last twenty-five years, 
and that of silver to that produced in the last eighty years. No 
one has as yet been able to satisfactorily explain what has be¬ 
come of all the rest of the precious metals. 

Only an estimate can be made of their wear and tear, which 
is an irretrievable loss, either in the abrasion of coin or in 
the use of leaf or of the pure metals for plating purposes. Add 
to this the amount lost in lead, copper, and other metals, which 
do not contain enough of it to separate, and it is not a matter of 
surprise that, notwithstanding the enormous yearly increase, the 
estimate of the total amount supposed to exist in the world 
during any period is not perceptibly greater. 

In all the methods for the extraction of the precious metals 
there are considerable losses. With the perfection of processes, 
the main object is to reduce them, or else to cheapen the labor 
of extracting the ores. These losses are greater than is usually 
supposed, because as a general rule systematic assays of the 
tails are not made. Yet it is known that the tails contain pre^ 
cious metals, and they are ‘sometimes re-worked with profit, 
especially those from the silver mines. An interesting investi¬ 
gation was made some years ago, the results of which are given 
below,^ showing the great loss in some of the mills. 



Yield of Ore 
in the Mill. 

Remaining in Tails. 

Total 
in Tails. 

Gold. 

Silver. 

At the mill. 

$18 60 

18 60 

3 50 

3 50 

$10 04 

5 02 

13 55 

8 79 

56 00 

$3 14 

3 92 

6 28 

6 28 

33 30 

$13 18 

8 98 

18 83. 

15 07 

89 00 

Same tailings 350 ft. from mill.... 
Average yield of 150 tons. 

( ( < ( H 

Slime from end of sluice 310 ft. long 



^ Report of the U. S. Mining Commissioner, 1872, p. 17. 



















THE METALLURGY OF GOLD AND SLLVER, 45 


It was also found that water from the mills three fourths of 
a mile below them contained in suspension, as an average of 
twelve assays, $0,018 per gallon. There were in this locality 
57^)000 gallons of this water flowing away in twenty-four hours, 
•or a loss of $339.84. It was estimated that the annual loss of 
two mills working 250 days in the year was $84,960. From 
these and similar data the conclusion is drawn, that the loss is 
between fifty and sixty per cent of the total yield of the ore. 

It is a matter of great interest to ascertain what the cause of 
these losses is, in order to learn how far they are capable of rem¬ 
edy. The first of these is undoubtedly a desire to get the largest 
possible output from the mill. This makes the ore too coarse to 
have all the gold and silver amalgamate, as part of it may not be 
released from the gangue. It would be much better to get the 
-output by a more careful sizing of the ore, not forcing the stamp 
to do the work of a Blake’s Crusher, and not sending to the 
mortars any ore fine enough to pass the screens. This is a 
matter of some importance, for it has been found with all kinds 
•of stamps using screens, that it takes just as long to get crushed 
-ore which has already passed the screens out of the mortar, as it 
does to crush and force it out. Too fine crushing is also quite 
as bad, for it produces “ float,” and is quite likely to put the pre¬ 
cious metals in a condition in which they will not amalgamate. 

Supposing that the losses which result from improper working 
•do not exist, there are a few causes of loss which do not always 
amount to much, but which, in the early days, were a source of 
•considerable loss. It has been found that anyhol.es in the cast¬ 
ings of the stamps, pans, etc., will attract the amalgam, and that 
it will even be carried into holes deep in the interior of the piece. 
This was a source of profit in the early days to those who recov¬ 
ered the precious metals when the worn out castings were melted. 
Another loss may be in cleaning the plates by taking off the 
amalgam too thoroughly. It is a well-known fact that new 
plates do not act as readily as old ones; the difference is so 
great, that when the mills can afford it, new plates are coated 
with gold or silver amalgam. Gold and silver will go much 
quicker to amalgam than to mercury. Too slow a current of 
water will keep the surface of the plates covered with a film 
of sand; a too rapid current will prevent the gold from being 
•caught. If the gold is attached to a piece of the gangue rock 
which is relatively large, the specific gravity may be so re¬ 
duced as to prevent the particles from coming in contact with 


46 THE METALLUEGY OF GOLD AND SILVER. 


the mercury. If the blankets are left too long without wash- 
ing, so that the hairs become charged, the fine particles of gold 
are lost. If all these causes of loss are avoided, there are still 
others. For if the mercury is not kept clean or made so by chem¬ 
icals, the “ quick,” having an extremely thin film upon it, does 
not act upon the gold or silver. Exactly the same effect is pro¬ 
duced to a small extent when the rock is soapy, as is the case with 
some of the magnesian and aluminous rocks. If there are too 
few amalgamating machines, if the sluices are too short, there is 
also a loss. A very important source of loss is the flouring of 
the mercury from too rapid motion, or from the too free use of 
chemicals. In such cases steam may be used, if it is live steam 
fresh from the boiler, which prevents flouring by the expansion 
of the globules. If steam from the engine is used as a matter 
of economy, it often increases the loss, as very minute particles 
of grease are always carried off with it, which coat the mercury. 
The cause of the losses on the concentrates has already been 
discussed. 



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